diff --git a/lib/exception_notifier/notifier.rb b/lib/exception_notifier/notifier.rb
index c55778c3..a225c82f 100644
--- a/lib/exception_notifier/notifier.rb
+++ b/lib/exception_notifier/notifier.rb
@@ -75,7 +75,7 @@ def background_exception_notification(exception, additional = {})
         @options = (@notifier.args.first || {}).reverse_merge(self.class.default_options)
         @exception = exception
         @backtrace = exception.backtrace || []
-        @additional_context = additional
+        @additional_context = additional.stringify_keys
         @sections  = %w(additional_context backtrace)
         subject  = compose_subject(exception)